硼酸镧玻璃的结构和热学性能研究

Thermodynamics properties and structure of lanthanum borate glass

通过高温熔融法制备了La_2O_3-B_2O_3-Zn O(简称LBZ)系微晶玻璃,利用差热分析(DSC)、红外光谱(IR)和X射线衍射(XRD)等测试手段,研究了LBZ微晶玻璃的玻璃形成区域、原子的配位状态和相组成。同时探讨了组分含量与微晶玻璃的热学性能、析晶性能之间的关系。结果表明:LBZ的玻璃形成区间(摩尔分数)La_2O_3为0~24.4%、B_2O_3为34%~78%、Zn O为0~63%;LBZ微晶玻璃的网络结构主要由[BO_3]和[BO_4]组成,La^(3+)作为网络修饰体存在于网络间隙中,Zn_2+作为中间体以[Zn O4]的形式处于网络结构之中或以[Zn O6]形式处于玻璃结构之外;LBZ玻璃经高温热处理后的主要晶相为La(BO_2)3和La BO_3;玻璃化转变温度随着La_2O_3和B_2O_3含量的增加而增加、随着Zn含量的增加而降低;La系玻璃的析晶激活能介于337~397 k J/mol,且随着La_2O_3含量的增加而增大。

A kind of La2O3-B2O3-ZnO（LBZ） glass-ceramics was prepared by high temperature melting technology. The differential scanning calorimetry（DSC）, infrared spectroscopy（IR） and X-ray diffraction（XRD） were utilized to analyze the glass forming region, the coordination state and the phase composition of the LBZ glasses. The effects of LBZ glass components on the thermodynamics properties, the variety of the main crystalline phases and the thermal properties were also studied. The experimental results show that： the LBZ glass is formed when the contents of La2O3, B2O3 and ZnO are 0~24.4%, 34%~78% and 0~63% （mole fraction）, respectively. The glass network structure is constituted with [BO3] units and [BO4] tetrahedra. The La3＋ locates in the gap of the network acting as network modifiers, and the Zn2＋ can either locate outside the network in the form of [ZnO6] or enter the network in the form of [ZnO4] acting as intermediate. The main crystalline phases of the LBZ glasses are La（BO2）3 and LaBO3 atter high-temperature heat treatment. The glass transition temperature is gradually elevated with the increase of La2O3 and B2O3 contents and the decrease of the ZnO content. The crystallization activation energy of the La-based LBZ glass is 337-397 kJ/mol and it is enhanced as the content of La2O3 is increased.